To prevent sludge and sewage from stormwater drains from flowing into the sea, Brihanmumbai Municipal Corporation (BMC) has planned in-situ treatment of sewage from the drains with the help of N-Treat Technology developed by IIT-B.

What is N-Treat technology?

• N-Treat is a seven-stage process for waste treatment that uses screens, gates, silt traps, curtains of coconut fibres for filtration, and disinfection using sodium hypochlorite.
• According to the detailed project report for N-Treat, it is a natural and environment-friendly way of sewage treatment.
• It’s setup takes place within the nullahs channels that is through the in-situ or on-site method of treatment, and does not require additional space.

What does the process involve?

(1) Screening

• The first stage involves screening to prevent the entry of floating objects such as plastic cups, paper dishes, polythene bags, sanitary napkins, or wood.
• IIT-B has proposed to install three coarse screens, the first with 60 mm spacing for removal of large floating matter, the second with 40 mm spacing, and the third with 20 mm spacing.

(2) Slit trap

• The second stage has proposed construction of a silt trap, which creates an inclination and ‘parking spot’ on the bed of the nullah for sedimentation.

(3) Bio zones

• The next three stages are installation of ‘bio zones’ in the form of coconut fibre curtains that will act as filters and promote growth of biofilm to help in decomposition of organic matter.
• A floating wetland with aquatic vegetation planted on floating mats has been proposed.

(4) Florafts

• Aside from a floating bed on the surface, IIT-B has proposed suspending floating rafts vertically, called florafts.
• Their hanging roots would provide a large surface area for passive filtration as well as development of microbial consortium.
• In the floating wetlands, plants acquire nutrition directly from the water column for their growth and development, thus reducing the organic as well as inorganic pollutants.
• The final stage for sewage treatment will include disinfection using sodium hypochlorite, to kill the bacteria in the water.

How will it be used by BMC?

• A senior civic official said: “BMC approached IIT-B to submit a Detailed Project Report for the project.
• The N-Treat method suggested to the civic body is cost-effective, as it does not require manual pumping, and saves electricity, and does not require extensive manpower for maintenance.”
• The floating matter will be removed daily, silt deposits from the silt traps will be removed once in four months, and plants will be trimmed as required.
• The floating matter collected every day will be disposed of at the nearest municipal waste collection point daily.

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